Support deploying Modal release to both channels

Author: anth-volk

.github/scripts/test_resolve_modal_release_config.py

@@ -62,6 +62,27 @@ def test_resolve_release_uses_workflow_dispatch_inputs():
     assert resolved.config.cleanup_target == "frontier"
 
 
+def test_resolve_release_accepts_both_workflow_dispatch_target():
+    resolved = resolve_release_from_event(
+        {
+            "inputs": {
+                "new_app_target": "both",
+                "promote_existing_frontier": "false",
+                "cleanup_target": "retired",
+            }
+        },
+        fetch_pr_body_for_commit=lambda _repository, _sha: None,
+        event_name="workflow_dispatch",
+    )
+
+    assert resolved.should_deploy is True
+    assert resolved.deploy_mode == "release"
+    assert resolved.config is not None
+    assert resolved.config.new_app_target == "both"
+    assert resolved.config.promote_existing_frontier is False
+    assert resolved.config.cleanup_target == "retired"
+
+
 def test_resolve_release_uses_weekly_default_for_empty_workflow_dispatch():
     resolved = resolve_release_from_event(
         {"inputs": {}},

.github/workflows/deploy-staged.yml

@@ -14,6 +14,7 @@ on:
         options:
           - frontier
           - current
+          - both
           - none
       promote_existing_frontier:
         description: "Move the existing frontier worker to current before deploying a new frontier"

changelog.d/1533.changed.md

@@ -0,0 +1 @@
+Allow Modal releases to launch the same newly built worker on both `current` and `frontier`.

docs/engineering/skills/modal-release-prs.md

@@ -24,7 +24,7 @@ modal_release:
 
 Allowed values:
 
-- `new_app_target`: `frontier`, `current`, or `none`
+- `new_app_target`: `frontier`, `current`, `both`, or `none`
 - `promote_existing_frontier`: `true` or `false`
 - `cleanup_target`: `none`, `retired`, `frontier`, or `current`
 
@@ -50,6 +50,20 @@ apps in the retired history are stopped after the manifest is updated. Use
 `cleanup_target: none` only when the user explicitly asks to preserve retired
 worker apps after release.
 
+Use this release shape when the newly built worker must become both `current`
+and `frontier` in a single release:
+
+```yaml
+modal_release:
+  new_app_target: both
+  promote_existing_frontier: false
+  cleanup_target: retired
+```
+
+This deploys one new worker app, writes the same app reference into both
+`current` and `frontier`, and moves the previous active workers into the
+manifest's `retired` history.
+
 Do not use PR labels, branch names, model-specific tags, or title prefixes to
 control Modal release behavior. The PR body YAML block is the source of truth.
 The PR-body YAML block is the only automatic signal that a deployment should

policyengine_household_api/modal_release/manifest.py

@@ -207,6 +207,22 @@ def apply_release_config(
         next_manifest["current"] = deepcopy(dict(new_app or {}))
         next_manifest["frontier"] = None
 
+    elif config.new_app_target == NewAppTarget.BOTH:
+        retired = _retire_entry(
+            retired,
+            next_manifest.get("current"),
+            retired_at=retired_at,
+            reason="replaced-current",
+        )
+        retired = _retire_entry(
+            retired,
+            next_manifest.get("frontier"),
+            retired_at=retired_at,
+            reason="replaced-frontier",
+        )
+        next_manifest["current"] = deepcopy(dict(new_app or {}))
+        next_manifest["frontier"] = deepcopy(dict(new_app or {}))
+
     next_manifest["retired"] = retired
     return validate_manifest(next_manifest)
 

policyengine_household_api/modal_release/release_config.py

@@ -38,6 +38,7 @@ class ModalReleaseConfigError(ValueError):
 class NewAppTarget(StrEnum):
     FRONTIER = "frontier"
     CURRENT = "current"
+    BOTH = "both"
     NONE = "none"
 
 

tests/unit/modal_release/test_manifest.py

@@ -84,6 +84,43 @@ def test_direct_current_release_retires_current_and_frontier():
     ]
 
 
+def test_both_release_sets_current_and_frontier_to_new_app():
+    manifest = {
+        "schema_version": 1,
+        "current": _app("current-app", us="1.690.0"),
+        "frontier": _app("frontier-app"),
+        "retired": [],
+    }
+    config = ModalReleaseConfig(
+        new_app_target=NewAppTarget.BOTH,
+        promote_existing_frontier=False,
+        cleanup_target=CleanupTarget.RETIRED,
+    )
+    new_app = _app("new-shared-app", uk="2.88.18")
+
+    updated = apply_release_config(
+        manifest,
+        config,
+        new_app=new_app,
+        timestamp="2026-01-02T00:00:00+00:00",
+    )
+
+    assert updated["current"] == new_app
+    assert updated["frontier"] == new_app
+    assert [app["app_name"] for app in updated["retired"]] == [
+        "current-app",
+        "frontier-app",
+    ]
+    assert [app["retirement_reason"] for app in updated["retired"]] == [
+        "replaced-current",
+        "replaced-frontier",
+    ]
+    assert cleanup_app_names_for_target(
+        updated,
+        CleanupTarget.RETIRED,
+    ) == ["current-app", "frontier-app"]
+
+
 def test_retired_cleanup_excludes_active_apps():
     manifest = {
         "schema_version": 1,

tests/unit/modal_release/test_release_config.py

@@ -29,6 +29,22 @@ def test_parse_modal_release_config_from_fenced_yaml():
     assert config.promote_existing_frontier is True
 
 
+def test_parse_accepts_both_target_without_promotion():
+    config = parse_modal_release_config_from_body(
+        """
+```yaml
+modal_release:
+  new_app_target: both
+  promote_existing_frontier: false
+  cleanup_target: retired
+```
+"""
+    )
+
+    assert config.new_app_target == NewAppTarget.BOTH
+    assert config.promote_existing_frontier is False
+
+
 def test_parse_rejects_missing_config():
     with pytest.raises(ModalReleaseConfigError, match="modal_release"):
         parse_modal_release_config_from_body("## Summary\n")
@@ -58,6 +74,20 @@ def test_parse_rejects_invalid_promotion_combination():
         )
 
 
+def test_parse_rejects_both_target_with_promotion():
+    with pytest.raises(ModalReleaseConfigError, match="may only be true"):
+        parse_modal_release_config_from_body(
+            """
+```yaml
+modal_release:
+  new_app_target: both
+  promote_existing_frontier: true
+  cleanup_target: none
+```
+"""
+        )
+
+
 def test_parse_rejects_active_cleanup_in_pr_config():
     with pytest.raises(ModalReleaseConfigError, match="may not be"):
         parse_modal_release_config_from_body(